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Abstract

As part of an European Community research programme telluric, magnetotelluric and geomagnetic deep sounding measurements were undertaken at 40 sites within the geothermal area of Travale. In the period range of 6- 10000 s the telluric field inside the Era graben is strongly polarized and directed + independent of the period + about parallel to the graben strike. The lateral variation of the telluric field amplitude is determined mainly by the distribution of the rocks (e.g., the central part of the geothermal anomaly inside the graben is correlated with a horst structure of resistive rocks) and an influence of the geothermal anomaly on the telluric field distribution cannot be observed. The apparent resistivity as well as the phase curves are rather similar at all sites within the graben exhibiting 4-4- OMEGAm for periods of 10 s and 50-500 OMEGAm for periods of 10000 s in E polarization. In the period range of 10 - 100 s the E- and B-polarization of magnetotelluric measurements can be interpreted by the 2-d effect of the Era graben while with increasing period the induced current system becomes more and more 3-d below all sites. This limits the determination of the sedimentary cover thickness (max. 2500 m) by 1-d and 2-d model calculations to periods of less than 100 s.

Additional information

Authors: BERKTOLD A J, LUDWIG-MAXIMILIANS-UNIVERSITAET MUENCHEN (GERMANY);DITTUS H J, LUDWIG-MAXIMILIANS-UNIVERSITAET MUENCHEN (GERMANY);EIGNER K H, LUDWIG-MAXIMILIANS-UNIVERSITAET MUENCHEN (GERMANY);TEUFEL U LUDWIG-MAXIMILIANS-UNIVERSITAET MUENCHEN (GERMANY), LUDWIG-MAXIMILIANS-UNIVERSITAET MUENCHEN (GERMANY)
Bibliographic Reference: EUR 10317 EN (1985) MF, 12 P., BFR 150, BLOW-UP COPY BFR 200, EUROFFICE, LUXEMBOURG, POB 1003
Availability: Can be ordered online
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